It is well known that the heat energy generated by the burning of wood in an interior fireplace is mainly lost because such heat energy rises in the flue associated with the fireplace and passes into the atmosphere. Only a small amount of the heat energy is radiated into the room in which the fireplace is located. While a fire in a fireplace gives the appearance of warming the room and the occupants of the room, it is clearly inefficient as a heat source.
To counter this loss of heat energy to the atmosphere, wood burning stoves have been used in or adjacent to fireplaces to burn wood or other fuel and to direct much of the generated heat energy laterally by radiation rather than vertically through a flue by convection. In this way, a stove in or adjacent to a fireplace can be a much more efficient heat source than can the fireplace used in a conventional manner.
A fire hazard arises when using a stove in a fireplace in that products of combustion rising from the stove through the flue adhere to the inner surface portions of the flue and these products are flammable at relatively low temperatures. This hazard presents an unsafe condition for the house or building containing the fireplace because sparks and flame can penetrate through cracks in the flue to adjacent wood and other flammable parts of the house or building and can cause fires. Because of this drawback, a need has arisen for improvements in the handling of combustion products emanating from a fuel-burning stove in a fireplace to assure a safer operation of the stove without sacrificing the efficient energy transfer characteristics of the stove itself.